Motion converting device



Feb; 1 6;, 1.965 G; K.. NEWELL MOTION CONVERTING DEV-ICE 4: Sheets-$heet 1.

Filed? F'eb. 28 1962 INVENTOR. Gearge K Newell A ttor ney Feb. 16, 1965 NEWELl 3,169,407

MOTION CONVERTING DEVICE Filed Feb. 28, 1962 4 Sheets-Sheet 2 INVENTOR.

' Georye K. Newell Attorney Feb. 16, 1965 s. K. NEWELL MOTION convsa'rms DEVICE 4 Sheets-Sheet 3 Filed Feb. 28, 1962 INVENTOR. Georg'e K Newell At torney Feb. .16, 1965 G. K. NEWELL.

MOTION CONVERTING DEVI/CE -4 Sheets-Sheet 4 Filed Feb. 28, .1962

INVENTOR fieorge K Newell A t t o rn ey United States Patent-O 3,169,407 MOTEON CGNVERTING DEVHIE George K. Newell, Level Green, Penn Township, Westmoreland County, Pa., assignor to Westinghouse Air Brake Qompany, Wilmerding, Pa., a corporation of Pennsylvania Filed Feb. 28, 1962, Ser. No. 176,362 9 Claims. (Cl. 74-4243) This invention relates to a motion converting device and more particularly to an improved motion converting device, of the screw and traveling nut type, characterized by anti-friction means between the traveling nut and screw.

Certain motion converting devices presently on the market include a threaded shaft and a traveling nut between which are a plurality of anti-friction bearing ele ments, such as balls, that are disposed in contact with corresponding threads or helical ball races formed respectively in the shaft and the traveling nut. In some of these motion converting devices the traveling nut is provided or fitted with one or more tubular ball guide members which interrupt the path of the balls, deflect them from the helical race, lead them diagonally across the outside of the traveling nut, and direct them back again into the ball raceway. This design forms a closed circuit through which the rolliru balls, as the medium of engagement between the threaded shaft or screw and the corresponding traveling nut, recirculate continually as the threaded shaft or screw and the corresponding traveling nut are rotated relative to each other. Consequently, the rotary motion is thus changed or converted to linear motion, or vice versa, with low friction loss.

Motion converting devices of the type mentioned above are all quite complicated and consequently the cost of manufacturing them is relatively high.

Accordingly, it is the general purpose of this invention to provide a simple, li htweight, efiicient, and relatively low cost motion converting device of the screw and traveling nut type capable of changing rotary motion to linear motion, or vice versa, with low friction loss and without using a tubular guide member to circulate the balls across the outside of the traveling nut.

According to the present invention, a preferred embodiment of a motion converting device comprises a hollow traveling nut and a shaft extending therethrough, the shaft having on its periphery a single or a multiple helical specially shaped thread which may be polygonal (or arcuate) in cross section and of a depth slightly less than that of the radius of a plurality of large bearing balls that are disposed therein for rollin contact therewith. The projecting halves of the bearing balls extend into corresponding cavities formed in the traveling nut. Each cavity in the traveling nut is provided with a plurality of smaller balls that constitute a ball bearing each of which smaller balls has rolling contact with the surface of the larger bearing ball and an annular tapered race formed on the interior of a dished cylindrical race member. An annular retainer member having a plurality of spaced-apart fingers is arranged between the balls of the ball bearing andthe annular tapered race. The fingers extend inwardly from the periphery of the annular retainer member with each finger disposed between two adjacent balls of the ball bearing. Each cylindrical race member is retained in its respective cavity in the traveling nut by a wedge-shaped snap ring that is inserted in a groove formed in the wall of the corresponding cavity in the traveling nut. Each large bearing ball cooperates with the specially-shaped thread in the shaft and with the smaller balls of the corresponding ball bearing to provide for rolling action therebetween, as the shaft is moved linearly in either direction without rotation on its longitudinal axis, to effect rotation 3,169,407 Patented Feb. 16, 1965 of the traveling nut if the traveling nut be restrained against longitudinal movement. Furthermore, if the traveling nut be restrained against rotation and a force applied thereto in a direction parallel to the longitudinal axis of the shaft, the shaft will be rotated with respect to the traveling nut as the traveling nut travels along the shaft in one direction or in an opposite direction corresponding to the direction of action of the applied force.

When the helical thread is polygonal in cross section, it provides for two spaced paths of simultaneous rolling contact between the ball and the shaft within the thread. The smaller balls of the ball hearing are so disposed with respect to the large bearing ball that the line of action of the thrust force between the traveling nut and the shaft passes through the center of one of the smaller balls, the center of the large bearing ball, and midway between the two paths of rolling contact between the ball and shaft.

' Also, the two adjacent sides upon which the corresponding large bearing ball rolls form a groove or cavity into which any foreign matter that may enter the thread may be pushed and thus prevented from hindering the rolling of the large bearing ball in the thread.

In the accompanying drawings:

FIG. 1 is a plan view of a motion converting device comprising a screw and a traveling nut with a portion of the traveling nut broken away to show one of a plurality of bearing balls disposed between the screw and the nut.

FIG. 2 is a vertical cross-sectional view of the screw and traveling nut shown in FIG. 1, taken along the line 22 of FIG. 1 and looking in the direction of the arrows, showing details of the specially-shaped helical polygonal thread formed in the periphery of the screw and the means for retaining a bearing ball between the screw and the nut.

FIG. 3 is a plan view showing a large bearing ball and its corresponding ball bearing in an assembled position in the thread formed in the screw with the traveling nut omitted for sake of clarity.

FIG. 4 is a vertical cross-sectional view, on an enlarged scale, taken along the line 4-4 of FIG. 3, showing the paths of contact between the large bearing ball and the screw, and the direction of the line of action of the thrust force transmitted from the screw to the large bearing ball.

FIG. 5 is a partial vertical cross-sectional view, on an enlarged scale, showing a second embodiment of a motion converting device similar to that of FIG. 4 but in which the helical thread in the shaft is arcuate in cross section.

FiG. 6 is a partial vertical cross-sectional view showing certain details of the screw and traveling nut of the second embodiment of the invention.

FIG. 7 is a vertical cross-sectional view of a fluid motor in which the second embodiment of the invention is used to convert linear motion of a piston to rotary motion of a shaft.

FIG. 8 is a vertical cross-sectional view, taken along the line 8-8 in FIG. 7 and looking in the direction of the arrows showing certain details not apparent in FIG. 7.

Description-FIGS. 1 to 4 Referring to FIG. 1 of the drawing, the motion conyer-ting device embodying the invention comprises a screw-threaded shaft 1, a hollow unthreaded traveling nut 2 through which the screw-threaded shaft 1 ex nends and a plurality of bearing balls 3 disposed between the screw-threaded shaft 1 and the hollow traveling nut 2.

While omitted from the drawings for simplicity and clarity, it will be understood that it is intended that the motion converting elements be suitably mounted in various ways by means well known, in order to utilize their functions either as a driving or a driven element. example, the screw-thrcaded shaft 1 may be mounted for rotation on its longitudinal axis and restrained against For. 7

shaft.

; not shown, then the shaft will be caused to move along its longitudinal axis correspondingly, in one direction or the opposite direction according to, the direction of' rotalongitudinal movement while the traveling nut 2'is re- V strained against'rotation but adapted to move along the longitudinal axis of the shaft 1. -With the motion coni verting elements so mounted, the threaded shaft 1 may be rotated by reversible power means, in which case the traveling n'ut2 will-travel correspondingly-in one direction or the 'opposite'direction depending onthe direction of rotation of the shaft. If,.on the other hand, a force J which the respective bearing balls :2

is applied longitudinally to the traveling nutt2, then the f threaded screw will be Caused to rotate correspondingly in one direction or the opposite direction depending upon the direction of application of the force to thevnut 2.

Also, it will be apparent that the-screw-(threaded shaft may be mountedso' as to be shiftable along its longitudinal axis and restrained against rotation while the tnavelingnut 2 is restrained against longitudinal movement andfree to rotate. In such case, if a force is applied to'shift the shaft longitudinally, then the nut 2 will rotate i'correspondingly in one direction or the other without displacement longitudinally along the axis of theshaft,

Operation V In the absence of a force acting on the screi -threaded shaft 1.in a directioncoinciding with its axis, the bearing balls 3 move from the position in which the one bearing ball: 3 is shown in FIG. 4 to a position in contact the root 12 of the respective thread groove in which the respective bearing balls 3 are disposed. As the respective bearing balls 3-move from the position shown FIG. 4 to the position inwhich the bottom of the respective beaning balls 3 contacts the root 12 ofythe thread in which the respective bearing ball is disposed, each respective bearing ballmoves out of contact with the corresponding inclined surface 14 and vertical surface 16 shown in FlG.4.

Let itbe supposed that the hollow traveling nut 2 is restrained against longitudinalniovement along the axis depending'on the direction of application of forceto the Also, if the nut is rotated, as by power means tion of the nut 2. l 7 More. particularly, the shaft 1 includes triple right-hand threads 4, 5 and 6 which areseparatedone from the other by a helical thread groove machined in the outer periphery of theshaft 1. Obviously, there may be any desired number of threads on the shaft, which may be left or right handed as is best suited to a particular situation. r a

As shown in FIG. 2, the hollow traveling nut 2 comapn'sesa hexagonal-shaped body 7 having a longitudiual of the screw-threadedshaftl' but may rotate aboutthis axis. Let'it be funther assumed that the screw-threaded shaft l is supported so that it may move in either direction along its longitudinal axis without rotation tnereaabout. If now .a thrust force is applied to the screwthreaded shaft 1 in the directionofthe arrow A shown in FIGS. 1 and 3; this thrust forceacting on the screwthr eaded shaft 1 will move the screw-threaded shaft 1' in the direction of the left hand along its longitudinal; axis without rotation on it'slongitudinal axis and thereby cause therespective bearing balls 3 to roll up the inclined bore S'extending therethrough, the diameter of the bore.

8 being slightly greaterthan the outside diameter ,of the screw threaded shaft 71-; The alternate sides of the hexagonal-shaped body 7 are provided with cavities each s of which comprises a bore 9 and a coaxial counterbore 10, the inner end of which forms :a shoulder 11.

As shown in FIG, 4, the crest of the right-hand threads 4 and 5 are separated by ahelical screw-thread groove that is polygonal in cross section. As shown in FIG. 4,

this helical thread groove has a root 12;from the oppo- 1 site ends of which extend inclined surfaces 13 and 14 Q which'intersect, respectively, ertical surfaces 15 and 16 1 so that the surfaces 12, 13,114, 15' and 16 form a polygonal groove in which one of the bearing balls 3 is disposed as i'llustrati'vely shown in FIG. 4. The polygonal groove cooperates with the bearing ball 3 disposed therein to form therebetween a cavity into which any foreign matand thusprevented from hindering the rolling. of the bearing ball. The bearing balls 3 are retained, in their respective thread grooves by a ball bearing which comprises a plurality of-small balls 17 which, as shown in FIGS. 3' and 4, are disposed about the respective largei'bearing ball 3; Each small ball .17 is spaced from an adjacent smallball 17 by one of a plurality of fingers 18 that a extend, downward from and at a 'rightangle to the periphery in FIG. ,4. I v

Asshown in, FIGS; 1,12, 3 and 4, the surface of the respective bearingballs 3 have rolling contact with the surface of the corresponding small balls 17, which small of an-aamular retaining member 19,'as-ShQWI1 surface 14 (FIG. 4) andout of contact with the corresponding thread root 12 until each of the respective bearing b alls 3 contacts the corresponding vertical surface 16 in which'pos/ition'one of the bearing balls 3 in shown in FIG. 4., In this position, each of the bearing ballsfa has i point contact withthe inclined surface 14 at a point 23 1 thereonand also point contact with the vertical" surface 16 at apoint 24 on this vertical surface. A

' a From the above, it is apparent that two components of the thrust force applied to the screw-threaded shaft 1 in the direction of air-row A are transmitted to the bearing ball 3 at 'thepoints 23 and 24. From viewing FIGS. 3 and 4, it will be understood that't-hese twoforce components are acting in a direction perpendicular to the cutting plane of line 4-4 in FIG. 3, and equidistant from a line a b shown in FIG. 4 as passing through the center of the bearing ball 3 andflone of, the small balls 17.

Therefore, these two'fo-rce components are elfective to rotate the bearing ball 3 shown in FIG. 4 about a line c-d which constitutes an axis of spin for the bearing ball 3 and which line cd,' as shown in FIG. 4, is at a I right angle to the line a-b. As the bearing ballS rotates I ter that'rnay enter the'thread groovejmay be pushed about its axis of spin, it rolls along two paths of contact in the correspondingthread groove in the screw-threaded shaft 1, the .point 23 on the inclined surface 14 lying on one of these paths and the point 24on the vertical surface 16 lying on the other of these paths.

From FIGS. '2, 3 and 4, it will be seen that the spherical surface of each of thebearin-g balls 3' has point conballs 17 are disposed in spaced-apart relation between the spherical surfaceof the respective bearing ball 3 and a dishedball race 20 (FIGS. 1 and 2), the inner end of which rests against a corresponding shoulder 11. Each of the dished ball races 20 is retained against the corresponding shoulderll by means of a tapered snap ring 21 that is inserted in a groove 22 machined in the wall of the corresponding counterbore 1Q.

tact with each of the small balls 17 of the corresponding ball bearing. Therefore, as each hearing-ball 3 rotates on its axis of. spin as it rolls along the two pathsof contact in its corresponding thread groove, it elfects' rotation of the small balls17 of the corresponding ball bearing soth-at these small balls 17 roll. around a ball' the axis of the screw-threaded shaft 1 without longitudinal movementv'along this axis since, as has been assumed,

the hollow traveling not 2 is restrained against longitudinal movement along this axis.

From the above, it is apparent that the motion converting device shown in FIGS. 1 to 4, inclusive, is capable of converting longitudinal movement of the screw-threaded shaft 1 in the direction of arrow A into rotary motion of the hollow traveling nut 2 about the longitudinal axis of the screw-threaded shaft 1.

Let it now be supposed that it is desired to convert linear movement of the hollow traveling nut 2 along the longitudinal axis of the screw-threaded shaft 1 into rotary motion of the screw-threaded shaft 1 about its longitudinal axis. Accordingly, let it be supopsed that the hollow traveling nut 2 is restrained against rotation about the longitudinal axis of the screw-threaded shaft 1 but may have linear movement in either direction along this axis. If now a thrust force is applied to the hollow traveling nut 2 in the direction of the arrow 3 shown in F163. 1 and 3, the force thus applied to the hollow traveling nut 2 is transmitted through the dished ball races 2% disposed in the counterbores in the hollow traveling nut 2 to each small ball 17:: shown in FIG. 3 carried in each dished ball race. The force thus transmitted to each small ball 17a acts in the direction of a line that lies in a plane that passes through the center of the respective small ball 17a and the center of the corresponding hearing ball 3. It will be noted from FIG. 3 that this plane does not pass through the two points 23 and 24 (FIG. 4) of contact between the bearing ball 3 and the corresponding thread groove in the screw-threaded shaft 1. Consequently, the direction of action of the force transmitted to the bearing balls 3 from the hollow traveling nut 2 is eiiective to cause the screw-threaded shaft 1 to rotate on its own axis since, as has been assumed, the hollow travel ing nut 2 is restrained against rotation. In other words, the force acting on each bearing ball 3 tends to roll it along the two paths of contact in the corresponding thread groove in the screw-threaded shaft 1 and thus around the screw-threaded shaft 1, but, since the hollow traveling nut 2 is restrained against rotation, the bearing balls 3 cannot thus roll around the screw-threaded shaft 1. Therefore, the bearing balls 3 effect rotation of the screw-threaded shaft 1 on its longitudinal axis and linear movement of the hollow traveling nut 2 dong this axis in the direction of the arrow B.

If a thrust force is applied to the hollow traveling nut 2 in the direction of the arrow A shown in FIGS. 1 and 3, the screw-threaded shaft 1 will be rotated on its longitudinal axis in a direction opposite to the direction of rotation effected by the thrust force acting in the direction of the arrow B.

Descrip!i0nFIGS. 5 and 6 FIGS. 5 and 6 of the drawings show a motion converting device that constitutes a second embodiment of the invention. This motion converting device comprises a screw-threaded shaft 25, a hollow traveling nut 26 through which the screw-threaded shaft 25 extends, and a plurality of spherical-ended plugs 2'7 each having a shank 28 that is press-fitted into an inner race 29 of a conventional ball bearing carried by the hollow traveling nut 26. Each of these ball bearings comprises, in addition to the inner race 29, an outer race 3% and a plurality of balls 31 disposed between the races.

As shown in FIG. 6, the hollow traveling nut 26 comprises a hexagonal-shaped body having a bore 32 extending therethrough, the diameter of the bore 32 being slight ly greater than the outside diameter or" the screw-threaded shaft 25. The alternate sides of the hollow hexagonalshaped traveling nut 26 are provided with cavities each of which comprises a bore 33, a counteribore 34, and a coaxial threaded counterbore 35. The inner end of the counter-bore 34 forms a shoulder 36 against which rests the lower side of the outer race 3% of the ball bearing. A threaded plug 37 is screw-threaded into the threaded countenbore 35 to retain the ball bearing races 29 and 3t) and the balls 31 in an assembled position.

The screw-threaded shaft 25 is of the multiple-threaded type which, for example, may include triple right-hand helical threads machined in the outer periphery thereof. As shown in FIG. 5, which corresponds to FIG. 4 of the first embodiment of the invention, these triple right-hand helical threads are separated by a thread groove 38 that is arcuate or send-circular in cross section, the radius of which semicircle is slightly greater than the radius of the spherical-ended plug 27 to provide a cavity into which any foreign matter that may enter the thread groove may be pushed and thus prevented from hindering the rotation of the spherical-ended plug 27 and the inner ball bearing race 29.

it is evident from FIG. 5 that when a longitudinal thrust force is applied to the screw-threaded shaft 25 in the direction of the arrow C, the spherical-ended plug 27 has point contact with the screw-threaded shaft 25 at a point 39 located at the upper right-hand end of the threaded groove 38 and the spherical-ended plug 27 rolls along a single path passing through the point 39 rather than along two paths as do the bearing balls 3 shown in FIGS. 1 to 4, inclusive. In all other respects, the operation of the second embodiment of the invention shown in FIGS. 5 and 6 is substantially the same as that of the first embodiment shown in FIGS. 1 to 4, inclusive, and need not be described in detail.

Descripti0nFIGS. 7 and 8 7 FIGS. 7 and 8 of the drawings show a motion translating device in the form of a fluid motor 40 embodying the structure shown in FIGS. 5 and 6. The fluid motor 4% may be adapted for a variety of uses, as for example, to effect the rocking of the brake lever in a unit brake assembly of the type described and claimed in the copending application or" George K. Nowell, Serial No. 167,690, filed in the United States Patent Qflice on Jan uary 22, 1962, now Patent No. 3,131,788, and assigned to the assignee of the present application.

The fluid motor 4t comprises a cup-shaped cylinder body 41 and a pressure head 42 between which is coaxially disposed a sleeve member 43. The open end of the cup-shaped cylinder body ll is provided with an outwardly extending annular flange 44 that has a shallow coaxial counterbore 4S and a plurality of arcuately spaced bores 46. One end of the sleeve member 43 is disposed in the counterbore 45 with an annular gasket 47 interbores 46 in the annular flange 44. The sleeve member 43 is rigidly clamped between the annular flange 44 and the pressure head 42 by a plurality of bolts 51 extending through the respective bores 46 in the annular flange 44 and having screw-threaded engagement with corresponding screw-threaded bores in the pressure head 42.

The cup-shaped cylinder body 41 is provided with a bottom bore 52 in which is slidably mounted a power piston 53 comprising two oppositely arranged packing cups 54 that are clamped between a flange 55 formed on one end of a hollow piston rod 56 and a follower member 57 by a plurality of cap screws 58, two of which are shown in FIG. 7. The power piston 53 cooperates with the cup-shaped cylinder body 41, the sleeve member 43 and the pressure head 42 to form on opposite sidesof the power piston 53 a pair of fluid pressure chambers 59 and oil to which fiuid under pressure can be supplied respectively through a conduit 61 secured to the pressure head 42. and a conduit 62 secured to the closed end of the cup-shaped cylinder body 41.

In order to prevent rotation of the power piston 53 forms a shoulder 67;

, her.

f the bores 65 is a counterbore 65 the innerend of which Resting against each of the shoulders 67 is an outer race 68 of a first ball bearing that also comprises an inner race 69 and a' plurality of balls 76 interposed between the inner and outer races. 7 p

- Press-fitted into each of the inner races 69 is a shank 71 of a spherical-ended, plug 72. Each of the first ball bearings is separated from an identical second ball hearing by an annular spacer member 73 also disposed in the respective counterbore 66. The respective two ball bear ings and correspondingannular spacer member 73 are" retained in the respective counterbore 66by a snap ring 74 that'is inserted in .a groove 75'forrned in' the wall of the respective counterbore es.

' The spherical-ended plug72 carried bythe inner race of each ofthesecond ball bearings is disposed in one of two diametrically opposite semicircular longitudinally extending grooves '76 and 77 formed in the interior wall of the sleeve member 43. It is clearly apparent from FIGS. 7 and 8 that these two diametrically oppositely arranged spherica -ended plugs 72 -an'd their corresponding grooves 76 and 7'7 will positively prevent rotation ofthe power piston 53 and the hollow piston rod 56 with respect to the.

cup-shaped cylindrical body 41 and the sleeve member 43 asthe power piston 53 is moved in one direction or in an opposite direction in response to the supply of fluid under pressure to one of the chambers 59 or 6%) and theventing of fluid under pressure from the other cham- 1 Extending into the open end of the hollow piston rod 56 is one end of ashaft 78 having a double helical righthandthread, arcuate in cross section, machined in the outer periphery thereof for a portion of itslength extending in the direction of the left hand, as viewed inFIG. 7,

from said one end to the right-handside of the pressure head 42. The remaining portion ofthe shaft 78 is unthreaded and of reduced diameter thereby forming a shoulder 79 at the left-hand end of the threaded portion of the shaft. I I

The spherical-ended plug 72 carried by the inner race 69' of each of the above-mentioned first ball' bearings is disposed in one of the two helical right-hand thread 8 Operation Let it -be assumed that fluid under pressure is completely vented fnomthe chambers 59 and 64 Further, assume that the power piston 53, the hollow piston rod56 and the shaft 78 occupy the position in which they are shown in FIG. 7 of the drawings. Let it now be assumed that fluid under pressure is supplied to the chamber 59 through the conduit 61 while the chamber 60 remains open to'atmosphere through the conduit 62. 'Fluid under pressure thus supplied to the chamber 59 acts on the left-hand face of the power piston 53 to move it in the direction of the right hand until the follower member 57 abutsthe right hand or closed end of the'cup-shaped cylinder body 41.

It is evident from FIG. '7 of the drawing that the fluid under pressure acting on the left-hand face of thepower piston 53 is'eifective, through the hollow piston rod 56;,

"the bosses 63 and 640a the left-hand end of thehollow piston rod 55, the outer races 68, balls 70, inner races 6?,

shanks 7 1 and the sperica-l-encled plugs 72 of each of the above-mentioned first ball bearings, to exert a thrust force in the direction of the right hand on the screw-threaded portion of the shaft 78 which iseifective, as expla'ined in connection with the'structure shown in FIGS; 5 and dot the drawings, to cause rotation of the shaft'78 in one direction about its longitudinal aids as the power piston 53 moves in the direction of the right hand.

, Let it now be supposed that fluid under pressure is vented from thechamber 59 through the conduit 61- to atmosphere while fluidunder pressure is simultaneously supplied to the chamber 60 through the conduit 62. Fluid under pressure thus supplied to the chamber 66) acts on theright-hand face of the power piston 53 to move it in thedirection of-the left hand until the bosses 63 and 64 carried on the left-hand end of the'hollow piston rod 56 abut the right-hand face of the pressure head 42..

It is likewise evident from FIG. 7that the fluid under pressure acting on the right-hand face of the power piston 53 is effective, through the hollow piston rod 56, the bosses 63 and 64 on the left-hand end of the hollow piston rod 56, the outer races 68, balls. 7%, inner races 69, shanks 7'1, and the spherical-ended plugs 72 of each of the abovementioned first ball bearings, to exert a thrust force in the direction of the left hand on the screw-threaded portion of the shaft 78 which is effective to cause rotation of the shaft 78 about its longitudinal axis in a direction opposite the above-mentioned one direction as the power piston 53 grooves machined in the shaft 78, as isshown in FIG. 7

of the drawings, to provide a driving connection between the power piston 53 and the shaft 78 whereby the rota- 7 tion of the shaft 78can be eflected in response to linear movement of the power piston 53 within the bottom bore 52in the cup-shaped cylinder body 41.

The unthreaded portion of the shaft 7 8 on the left-hand side of the shoulder 79 extends through aborefit) in the 7 pressure head 42 and is rotatably mounted in a pair of identical spaced-apart ball bearings carried respectively in coaxial counterbores 81 and 82 extending inward from moves in the direction of the left hand.

a =Fromthe above, it is apparent that the supply of fluid under pressure to the one or the other face of the power piston '53 is eifective' to move the power piston 53 in a corresponding direction to cause the shaft 78 to rotate in one direction or in 'an-opp'osite direction about its longitudinal axis. V

' \As hereinbefore stated, FIGS. 7 and 8 of the drawings show a motion translating device in the form of a fluid motor 40 embodying the structure shown in FIGS. Sand 6.

It should be understood, however, that the structure disclosed ill FIGS. 1 to 4, inclusive, of the drawings can be the opposite faces of the pressure head. Each ofthese ball bearings comprises an outer race 83 press-fitted into one of the counterbores 81 and $2, an inner race 84 press-fitted onto the reduced portion of the shaft 78, and

a plurality of balls 85 interposed between the respective inner and outer races so as to have rolling contact therewith 'as the shaft 78 is. rotated about its longitudinal axes.

Leakage from the chamber 59 along the shaft 78, {which extends through the bore 80 in the pressure head 42 to the exterior "of the fluid motor 40, is prevented by a resilient gasket ring 86 disposed in surrounding relation to the periphery of the unthreaded portion ofthe shaft 78 and in a groove 87 formed in the pressure head 42in coaxial relation to the bore 80. 5

used in the fiuid motor 40 in lieu of the structure shown in FIGS. Sand 6 if desired.

Having .now described the invention, what -I claim as new and desire to secure by Letters Patent is;

1. A motion converting mechanism comprising: (a) a hollow unthreaded nut havinga radial aperture therein, a

' (b) a bearing member comprising a plurality of balls,

the centers of said balls lying in a circle, said bearing member being removably carried in said radial aperture,

(c) a shaft disposed within saidhollow unthreaded nut and having thereon a helical groove, the cross section of which has at least two intersecting sides forming an angle, the bisector of which passes through a point on the circumference of the circle passing through the centers of the balls of said bearing member, and (d) a sphere rotatably mounted in said bearing memher and having a portion thereof disposed in said helical groove on said shaft for rolling contact with two paths of point contact, each of which paths is on a separate one of two adjacent sides whereby, with said hollow unthreaded nut restrained against rotation and said shaft restrained against movement along its longitudinal axis, upon the exertion of a longitudinal thrust force to said hollow unthreaded nut in either direction, said sphere effects rotation of said shaft about its longitudinal axis, and upon rotation of said shaft in either direction about its longitudinal axis, said sphere transmits a force to said hollow unthreaded nut to cause said nut to travel correspondingly and longitudinally along said shaft. 2. A motion converting mechanism, as claimed in claim 1, further characterized in that with said hollow unthreaded nut restrained against movement along the longitudinal axis of said shaft and said shaft restrained against rotation in either direction about its longitudinal aixs, the exertion of a longitudinal thrust force on said shaft in either direction causes movement of said shaft along its longitudinal axis to transmit, via said sphere, a force to said hollow unthreaded nut to eifect rotation thereof about the longitudinal axis of said shaft, and rotation of said hollow unthreaded nut about the longitudinal axis of said shaft in either direction will transmit, via said sphere, a force to said shaft to cause longitudinal movement of said shaft, without rotation, in a corresponding direction along its axis.

3. A motion converting mechanism, as claimed in claim 1, further characterizing in that the portion of said sphere that is disposed in said helical groove on said shaft for rolling contact with two paths of point contact each of which paths is on a separate one of two adjacent sides of said helical groove, rolls along said paths on said two adjacent sides with substantial clearance therebetween and the remaining sides of said helical groove.

4. A motion converting mechanism, as claimed in claim 1, further characterized in that the diameter of said sphere is greater than the diameter of said balls of said bearing member.

A motion converting mechanism, as claimed in claim 1, further characterized in that the bisector of the angle formed by two of said intersecting sides of said helical groove passes through the center of said sphere.

6. A motion converting mechanism, as claimed in claim 1, further characterized in that said sphere has rolling contact with the surface of the balls of said bearing member.

7. A motion converting mechanism comprising: (a) a hollow unthreaded not having a plurality of spaced-apart radial apertures therein, (12) a plurmity of bearing members each comprising a plurality of balls, the centers of said balls lying in a circle, and each bearing member being removably carried in a corresponding one of said apertures, (c) a shaft disposed within said hollow unthreaded nut and having thereon a plurality of uniformly spaced helical grooves of the same pitch, the cross section of each groove having a plurality of sides, two of which adjacent sides intersect to form an angle, the bisector of which passes through a point on the circumference of the circle passing through the centers of the balls of a corresponding bearing member, and (d) a plurality of spheres, each rotatably mounted in a corresponding bearing member and having a portion thereof disposed in a corresponding one of said plurality of helical grooves for rolling contact with two paths of point contact, each of which paths is on a separate one of two adjacent sides of the corresponding one of said plurality of helical grooves whereby, with said hollow unthreaded nut restrained against rotation and said shaft restrained against movement along its longitudinal axis, upon the exertion of a longitudinal thrust force to said hollow unthreaded nut in either direction, said spheres effect rotation of said shaft about its longitudinal axis, and upon rotation of said shaft in either direction about its longitudinal axis, said spheres transmit a force to said hollow unthreaded nut to cause said nut to travel longitudinally along said shaft.

8. A motion converting mechanism comprising:

(a) a cup-shaped cylinder including a pressure head sealingly secured thereto in coaxial alinement therewith, said cup-shaped cylinder having at least one longitudinally extending groove therein,

(b) a shaft coaxial with said cylinder and mounted in the pressure head of said cylinder for rotation around its longitudinal axis while restrained against linear movement therealong, said shaft having thereon at least one helical groove,

(0) a hollow unthreaded traveling nut comprising a sleeve into which said shaft extends, said sleeve having integral therewith at one end at least one hollow boss and at the opposite end a power piston secured thereto for slidable movement in said cup-shaped cylinder in response to differential fluid pressure acting thereon,

(d) means carried in said hollow bosses, and cooperating with the longitudinal extending grooves in said cup-shaped cylinder for restraining the power piston of said hollow unthreaded traveling nut against rotation within said cup-shaped cylinder while said piston moves linearly in one direction or in an opposite direction, and

(e) a rotatable rnember carried in each of said hollow bosses and each including a spherical portion which extends into one of the helical grooves in said shaft to effect rotation of said shaft about its longitudinal axis without linear movement thereof along said longitudinal axis.

9. A motion converting mechanism comprising:

(a) a cylinder including a cup-shaped member, a sleeve and a pressure head sealingly secured together in coaxial alinement, said sleeve having two internal diametrically disposed longitudinally extending grooves therein,

(b) a shafit coaxial with said cylinder and mounted in the pressure head 20f said cylinder for rotation around its longitudinal axis while restrained against linear movement therealong, said shaft having thereon two parallel, spaced-apart helical grooves,

(c) a hollow unthreaded traveling nut comprising a sleeve into which said shaft extends, said sleeve having integral therewith at one end two diametricaL ly opposite hollow bosses and at the opposite end a power piston secured thereto for slidable movement in the cup-shaped member of said cylinder in response to the supply of fluid under pressure to one side thereof while the opposite side is open to atmosphere,

(d) a pair of identical, spaced-apart bearing members disposed in each of the :hollow bosses at one end of said sleeve, each bearing member having an outer race which is fixed in the respective hollow boss and an inner race rotatably mounted with respect to said outer race, and

(e) a pair of oppositely extending spherical-ended plugs for each one of said pair of spaced-apart bearings, each of said plugs having a shank press-fitted into a respective one of the inner races 0f the re spective pair of spaced-apart bearing members for rotation therewith, whereby the external ones of said spherical-ended plugs are disposed respectively in the two internal diametrically opposite longitudinal grooves in the sleeve of said cylinder and the internal ones of said spherical-ended plugs are dis- 1 1 posed respectively in the two parallel, spaced-apart helical grooves on'said shaft for rolling contact (them- 7 Within response to the supply of fluid under pressure to one or to the other side of the power piston to cause said spherical-ended plugs to effect rotation of said shaft about its longitudinal axis in one direction or in an opposite direction as the internal ones of said spherical-ended plugs roll along the two parallel, spaced-apart helical grooves on said shaft.

References Cited in the'fileof this patent UNITED STATES PATENTS Twyman m.-. June 30, 1936 Hogan et al. "Aug. 19, 1958 Beatty et a1. Nov. 6, 1962 V FOREIGN PATENTS 7 Italy Nov. 17, 1954 France June 24, 1957 

1. A MOTION CONVERTING MECHANISM COMPRISING: (A) A HOLLOW UNTHREADED NUT HAVING A RADIAL APERTURE THEREIN, (B) A BEARING MEMBER COMPRISING A PLURALITY OF BALLS, THE CENTERS OF SAID BALLS LYING IN A CIRCLE, SAID BEARING MEMBER BEING REMOVABLY CARRIED IN SAID RADIAL APERTURE, (C) A SHAFT DISPOSED WITHIN SAID HOLLOW UNTHREADED NUT AND HAVING THEREON A HELICAL GROOVE, THE CROSS SECTION OF WHICH HAS AT LEAST TWO INTERSECTING SIDES FORMING AN ANGLE, THE BISECTOR OF WHICH PASSES THROUGH A POINT ON THE CIRCUMFERENCE OF THE CIRCLE PASSING THROUGH THE CENTERES OF THE BALLS OF SAID BEARING MEMBER, AND (D) A SPHERE ROTATABLY MOUNTED IN SAID BEARING MEMBER AND HAVING A PORTION THEREOF DISPOSED IN SAID HELICAL GROOVE ON SAID SHAFT FOR ROLLING CONTACT WITH TWO PATHS OF POINT CONTACT, EACH OF WHICH PATHS IS ON A SEPARATE ONE OF TWO ADJACENT SIDES WHEREBY, WITH SAID HOLLOW UNTHREADED NUT RESTRAINED AGAINST ROTATION AND SAID SHAFT RESTRAINED AGAINST MOVEMENT ALONG ITS LONGITUDINAL AXIS, UPON THE EXERTION OF A LONGITUDINAL THRUST FORCE TO SAID HOLLOW UNTHREADED NUT IN EITHER DIRECTION, SAID SPHERE EFFECTS ROTATION OF SAID SHAFT ABOUT ITS LONGITUDINAL AXIS, AND UPON ROTATION OF SAID SHAFT IN EITHER DIRECTION ABOUT ITS LONGITUDINAL AXIS, SAID SPHERE TRANSMITS A FORCE TO SAID HOLLOW UNTHREADED NUT TO CAUSE SAID NUT TO TRAVEL CORRESPONDINGLY AND LONGITUDINALLY ALONG SAID SHAFT. 